Releasable zero backlash passive locking mechanism for a vehicle mounted rotary camera mast

Abstract

A rotary locking joint that has zero backlash is provided to secure a camera mast mounted on a vehicle in a deployed position. The joint is passive to lock while being easily releasable. The joint prevents rotation of the mast in one direction, with a hard stop element that prevents further rotation of the mast in the opposite direction. The locking joint includes a pawl member configured to rotate about a pawl rotation axis. The pawl member is maintained in place in the locked position via a torsion spring to ensure contact with a base portion of the mast. To release the joint, the pawl member is rotated in the opposite direction to remove a geometry interference condition. A sensor is arranged to detect whether the pawl member is in an unlocked position relative to the mast.

The invention claimed is: 
     
       1. A system for mounting to a vehicle, the system comprising:
 a mast structure having a mast and a support frame secured to the mast, the support frame arranged for affixation to a vehicle; and 
 a locking mechanism, comprising:
 a mast stop member configured for affixation to the mast structure, the mast stop member including at least one receptacle arranged along a first axis, the mast stop member having a first surface that prevents the mast from rotating in a first direction; 
 a pawl member having a first end, a second end remote from the first end, and a receptacle disposed between the first end and the second end, the first end being configured to releasable engage a surface of the mast, the receptacle being aligned with the at least one receptacle of the mast stop member along the first axis, and the second end being configured to selectively disengage the first end of the pawl member from the surface of the mast so that the mast is rotatable about a second axis different from the first axis, wherein rotation about the second axis is only permitted in a second direction opposite the first direction; 
 a shaft member received by the at least one receptacle of the mast stop member and the receptacle of the pawl member along the first axis; and 
 a torsion spring received along the shaft member and coupling to the pawl member, the torsion spring securing the first end of the pawl member against the surface of the mast in a deployed state with zero backlash. 
 
 
     
     
       2. The system of  claim 1 , the locking mechanism further comprising a sensor member, the sensor member having a sensor bracket and a sensor affixed to the sensor bracket, the sensor being configured to detect whether an engagement member of the pawl member is in adjacent proximity to the sensor bracket to indicate that the pawl member is in an unlocked position relative to the surface of the mast. 
     
     
       3. The system of  claim 1 , wherein the second end of the pawl member comprises an elongated handle. 
     
     
       4. The system of  claim 1 , wherein in the deployed state the mast has a first alignment substantially perpendicular to a roof surface of the vehicle or to a ground surface, and the first alignment is maintained with the first end of the pawl member secured against the surface of the mast. 
     
     
       5. The system of  claim 4 , wherein in a disengaged state the first end of the pawl member does not contact the surface of the mast. 
     
     
       6. The system of  claim 5 , wherein in the disengaged state the mast is rotatable from the first alignment to a second alignment, the second alignment being between about 90-120° relative to the first alignment. 
     
     
       7. A method of operating a zero backlash locking assembly, the method comprising:
 detecting that a pawl assembly of the locking assembly is in a locked position relative to an elongated mast; 
 upon detecting the locked position, raising the elongated mast from a stowed position to a deployed position; and 
 automatically locking the mast in the deployed position by impinging a first end of the pawl assembly against a surface of the elongated mast, wherein a torsion spring secures the first end of the pawl assembly against the surface of the mast with zero backlash. 
 
     
     
       8. The method of  claim 7 , further comprising actuating a handle of the pawl assembly in a direction to disengage the first end of the pawl assembly from the surface of the elongated mast, wherein upon disengagement the pawl assembly is temporarily retained in an unlocked state. 
     
     
       9. The method of  claim 8 , further comprising, upon disengagement and the pawl assembly being retained in the unlocked stated, rotating the elongated mast from the deployed position to the stowed position.